A heat-pump type air conditioner using a fin tube type heat exchanger constituted by fins arranged at certain intervals, between which a gas (air) flows, and heat transfer tubes which have spiral grooves on their inner faces, perpendicularly pierce each of the fins and a refrigerant flows inside, is known.
The air conditioner is generally provided with an evaporator for evaporating the refrigerant and cooling air, water and the like by evaporation heat at that time; a compressor for compressing the refrigerant discharged from the evaporator, raising its temperature and supplying it to a condenser; the condenser for heating the air, and water and the like by heat of the refrigerant; an expansion valve for expanding the refrigerant discharged from the condenser, lowering its temperature and supplying it to the evaporator, and a four-way valve for switching between a heating operation and a cooling operation by switching a direction in which the refrigerant in a refrigerating cycle flows. In addition, the heat transfer tube is incorporated in the condenser and the evaporator so that the refrigerant containing refrigerating machine oil flows inside thereof (See Patent Document 1, for example).    [Patent Document 1] Japanese Patent Laid-Open No. H6-147532 (FIGS. 1 and 13)